Synthesis of Dimethyl Carbonate from Urea and Methanol over ZnO

Abstract

The synthesis of dimethyl carbonate (DMC) from urea and methanol was investigated, to explore the catalysts and reaction conditions. Among the catalysts, ZnO showed the highest catalytic activity toward DMC synthesis. Based on the experimental investigation, the reaction conditions over ZnO for a batch process were optimized, and the highest DMC yield attained (based on urea) was ∼30%, because of the presence of side reactions. In addition, the reusability test indicated that ZnO had high stability.

One-Pot Synthesis of Dialkyl Hexane-1,6-Dicarbamate from 1,6-Hexanediamine, Urea, and Alcohol over Zinc-Incorporated Berlinite (ZnAlPO4) Catalyst

“…At the same time, the catalytic formation of both 3 and 5 via reaction of urea by alcoholysis and ammonolysis, respectively, have also been developed [19,24,25]. In other words, during the one-pot synthesis of dibutyl hexane-1,6-dicarbamate from HDA, urea and butanol, there may be two different reaction intermediates, i.e.…”

“…In fact, it is reported that the Lewis acidic catalysts, i.e. ZrO 2 , ZnO and La 2 O 3 , were employed to promote the catalytic activation of urea by both the ammonolysis and alcoholysis [18,19,26,27,31]. Considering the greater ability of Zn(II) in ZnAlPO 4 to attract electrons than ZnO, for the one-pot production of dibutyl hexane-1,6-dicarbamate from urea, HDA and butanol with ZnAlPO 4 as a catalyst, the coordination of the carbonyl oxygen of urea to Zn(II) as an key active intermediate species is formed.…”

“…dibutyl carbonate (3) and butyl carbamate (4), identified in the present work, might be a result of a nucleophilic attack of the butoxyl groups of the butanol on the carbonyl carbon in urea, as shown in Scheme 3. Because of the ambient electrophilicity, urea may react with not only the amines but also the alcohols [18,19,31]. In fact, it has been reported that both dialkyl carbonate and alkyl carbamate can be synthesized via the Scheme 2.…”

“…Because of the ambient electrophilicity, urea may react with not only the amines but also the alcohols [18,19,31]. In fact, it has been reported that both dialkyl carbonate and alkyl carbamate can be synthesized via the alcoholysis of urea with the corresponding alcohol using ZnO as a catalyst [19,31].…”

“…Because of the ambient electrophilicity, urea may react with not only the amines but also the alcohols [18,19,31]. In fact, it has been reported that both dialkyl carbonate and alkyl carbamate can be synthesized via the alcoholysis of urea with the corresponding alcohol using ZnO as a catalyst [19,31]. Meanwhile, in our work, using ZnAlPO 4 , its higher electron-attracting ability of Zn(II) than that in ZnO as a catalyst, the byproducts of both 3 and 4 were also formed from the excess of urea and butanol, further resulting in the increased selectivities of all products (1-6) on the basis of the amount of HDA converted more than 100%, as seen.…”